1. Field of the Invention
This invention relates to a webbing lock device for locking as necessary an occupant restraining webbing used in a seatbelt system for protecting an occupant in the event of an emergency situation, and particularly to a webbing lock device wherein an intermediate portion of the webbing is directly clamped for locking.
2. Description of the Prior Art
In the webbing retractors commonly used in seatbelt systems, even after the webbing winding rotation of a takeup shaft of a retractor has been locked, a considerable length of the webbing is unwound from the retractor until the webbing is tightly wound around the takeup shaft in layers since the webbing is usually relatively wound around the takeup shaft in a non-tight condition. Because of this, there has been proposed a webbing lock device in which an intermediate portion of the webbing is directly clamped by utilization of a tensile force of the webbing when the tensile force increases in value.
The abovementioned webbing lock device is adapted to clamp the intermediate portion of the webbing by means of a pair of corrugated surfaces. These corrugated surfaces are caused to close the interval therebetween to clamp the webbing where the interval therebetween at the side of the occupant restraining portion is wider than that at the side of the takeup shaft, whereby the tensile force of the webbing progressively decreases from the side of the occupant restraining portion to the side of the takeup shaft.
However, with the conventional webbing lock device of the type described, a pair of corrugated surfaces each having a predetermined curvature are merely inclined, whereby the interval between the opposing corrugated surfaces discontinuously varies, so that there exists a portion where the interval partially decreases. Consequently, in this webbing clamping portion where the interval partially increases, so that the webbing is not effectively clamped between the entire corrugated surfaces.